As regards the technical functional principle the synchro resolver is a rotating (magnetic) transformer whose output voltage is in an unequivocal relationship with the position of its shaft. For this reason, synchro resolvers are suited as absolute angle transmitters with an angular range of more than 360°, cf. in this connection e.g. DE-C-196 35 040 (Litton), column 1, lines 15 to 20 and column 2, lines 9 to 13. While the referenced publication relates to the merely mechanical construction of the synchro resolver, cf. FIG. 2 thereof, the determination of the desired system magnitudes is also possible with DE-C 38 34 384 (Lenze). The latter publication describes a process and a circuit arrangement for generating digitized rotational speeds and information on angles of rotation by means of a synchro resolver. In this connection reference is made to FIG. 1 thereof. It shows a control circuit as a servo controller, with which an operating signal of the rotor winding of the resolver is supplied to the circuit arrangement which controls the actuating variable to zero with a controller. Then, the output of the controller corresponds to the rotational speed in the stationary state and its integral corresponds to the position (called “angular output” there).
In particular, in the case of a rough environment, but also during long-term use, it must be ensured that the drives do not adopt any inadmissible operating conditions, i.e. that they do not experience any rotational speeds that are too high, if e.g. the measuring element for the measurement of the rotational speed fails such as due to an electrical or mechanical defect in the rotary encoder. Mostly, such problems are solved in the prior art by means of redundance, namely by the use of several rotary encoders, which, then, allow a safety monitoring within the framework of a comparative measurement or a voter-basis decision (at least in the case of three sensors).
Some embodiments allow non-redundant safety, and provide this safety for operating signals in drive technology. No additional sensors for said operating signals are to be added and, nevertheless, a safety-oriented limitation of the rotational speed of a drive is provided to obtain high levels of protection.